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Income taxes - Narrative (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019
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Business Acquisition [Line Items] |  |
Acquired net operating losses | $ 1,753 | $ 0
Franklin Financial Network, Inc. |  |
Business Acquisition [Line Items] |  |
Acquired net operating losses | $ 8,346 |

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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible domestic operating loss carryforwards. Excludes state and local operating loss carryforwards. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32632-109319 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32621-109319 + Details
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